Given the Kingdom Hearts series' child-friendly presentation, most players will assume its villains are somewhat lacking in terms of how evil they are. While this is an accurate assumption for Disney characters like Captain Hook and the Queen of Hearts, there are a few villains scattered throughout each entry who prove to be deserving of the title.
Most of the best Kingdom Hearts villains are original Kingdom Hearts characters, but there have been a few exceptions to this rule. While Disney villains may not always pose the greatest threat, some go to just as ruthless lengths as the series' original antagonists.
10 Clayton - Kingdom Hearts 1
The Kingdom Hearts series is home to some seriously ruthless villains, and though most of them are original characters, there are a few equally ruthless Disney additions. In Tarzan, Clayton is evil, but his Kingdom Hearts counterpart is on a completely different level.
Clayton spends most of Sora's visit to Deep Jungle tracking down the gorillas hiding in the jungle. Whenever he finds them, he raises his shotgun and fires, but thankfully, he never manages to get a clear shot. It's one thing to take aim at a gorilla, but to relentlessly fire at a fourteen-year-old boy and his pet dog and duck is something else entirely.
9 Maleficent - Kingdom Hearts 1
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Maleficent was the primary antagonist of Kingdom Hearts 1 until Ansem revealed himself during the final segment of the game. While Ansem wanted to submerge the worlds in darkness, all Maleficent wanted was to rule over as many worlds as she could.
To achieve this, she kidnapped the Seven Princesses of Heart and planned to use them to gain access to the heart of all worlds. If her plan wasn't thwarted by Sora, Donald, and Goofy during their visit to Hollow Bastion, she may very well have killed the princesses and taken over the galaxy. Though she has since become less of a threat to Sora and his companions, she was once Kingdom Hearts' ultimate villain.
8 Young Xehanort - Kingdom Hearts: Dream Drop Distance
Young Xehanort makes his debut appearance in Kingdom Hearts: Dream Drop Distance after his future self tasks him with assembling a new Organization 13. He spends most of the main story trailing after Sora and Riku during their Mark of Mastery exam, but his true goal is only revealed during the game's climax.
Young Xehanort's whole purpose in Dream Drop Distance was to lure Sora into the depths of sleep. Doing so would make him easy to possess while permitting the Organization to use him as its thirteenth member. When this failed, Young Xehanort was forced to find a replacement. He ventured to the Toy Box world in Kingdom Hearts 3 and split the world in two, submerging one-half in darkness. It was an evil experiment, but Young Xehanort seemed to derive great pleasure from ruining Buzz and Woody's lives.
7 Saix - Kingdom Hearts 2
For the majority of Kingdom Hearts 2, Saix acts as Xemnas' right-hand man. As a Nobody, he is unable to feel emotion, but he remembers what it was like. He reveals this to Sora during their encounter in Twilight Town before explaining that he knows how to injure a heart.
Saix joined the Organization in the hope that he might one day reclaim his heart. It seemed like a justifiable pursuit at first, but he did some truly terrible things to ensure he succeeded. He is a skilled manipulator who often uses deception to get his way.
6 Vanitas - Kingdom Hearts: Birth By Sleep
Vanitas came into existence when Master Xehanort extracted the darkness in Ven's heart and gave it physical form. As a result of this experiment, Ven was left with nothing but light in his heart, while Vanitas' heart contained only darkness.
After his birth, Vanitas aligned himself with Master Xehanort and vowed to help him summon Kingdom Hearts. His primary role was to rejoin with Ventus' heart to create the X-blade, and though he eventually achieved it, he spent most of the time beforehand following Aqua and Ven on their journey. Whenever he got the chance, he would mock the pair's friendship and berate them for relying on each other. He was needlessly cruel, considering what his role was, but that's what made him so memorable.
5 Larxene - Kingdom Hearts: Chain Of Memories
While most Kingdom Hearts villains tend to have a reason for their actions, Larxene seems to just enjoy what being evil feels like. She makes her first appearance in Kingdom Hearts: Chain of Memories, where she, alongside Marluxia, antagonizes Sora during his time in Castle Oblivion.
Not only is Larxene a ruthless villain, but she may also be the series' most condescending and vindictive character to date. When she's not outright deceiving Sora by planting false memories in his head, she will likely be seen mocking (and sometimes betraying) her comrades. If not for her surprising fondness for Marluxia, she would easily be the most ruthless character in the series.
4 Baldr - Kingdom Hearts: Dark Road
Baldr, first introduced in Kingdom Hearts: Dark Road, is one of the most ruthless villains in the entire series. After the death of his sister Hoder, Baldr locked himself up in his room, unknowingly allowing darkness to sink into his heart.
Under the control of a powerful darkness, Baldr launched an attack on Scala ad Caelum. He murdered eleven Keyblade wielders and planned to do the same to Xehanort and Eraqus. Thankfully, Xehanort managed to defeat him, but there is no way to undo the damage Baldr did.
3 The Master Of Masters - Kingdom Hearts: Union X [Cross]
Though frighteningly little is known about the Master of Masters, he is destined to become the next major antagonist of the Kingdom Hearts series. Like Xehanort, the Master lost a lot of his friends to the darkness. He mentions this to Luxu in Kingdom Hearts: Union X [Cross], before revealing his true intentions to him.
Instead of fighting the darkness head-on, the Master used his apprentices as bait. He manipulated them into fighting one another, making it easy for darkness to seep into their hearts. True Darkness cannot be destroyed in its original form, but it can be injured if it takes control of someone's body. The Master, aware of this, chose to trap the True Darknesses inside his students. If it means he can rid the world of these Darknesses, the Master is willing to sacrifice even his closest friends.
2 Xigbar - Kingdom Hearts 2
The secret ending of Kingdom Hearts 3 revealed that Xigbar was never who he claimed to be. He was once known as "Luxu" but has since abandoned that name in favor of "Xigbar." Changing names is one thing, but sacrificing countless people to obtain a new form is something else entirely.
Since his time as Luxu, Xigbar has undergone a series of bodily changes. Though it has yet to be confirmed, many believe he took control of Brain's body during the climax of Kingdom Hearts: Union X [Cross]. In Kingdom Hearts: Dark Road, he took over Bragi's body and used it to infiltrate Scala ad Caelum. Not only has he ruined the lives of these people, but he has also stolen their lives for himself.
1 Xehanort - Kingdom Hearts: Birth By Sleep
Xehanort is the source of most of Kingdom Hearts' villains. He first appeared in Kingdom Hearts 2, where he assisted Ansem the Wise in his research of the heart, but he wasn't always a dedicated researcher.
Before coming to Hollow Bastion, Xehanort was an aged man with two goals: summon Kingdom Hearts and purge the world of both light and darkness. To achieves these goals, he murdered his best friend, Eraqus, took possession of Terra's body, and eventually stole the hearts of all his fellow researchers, even little Ienzo, who was no more than a small child at the time. Though his reasoning was later revealed to be somewhat noble, the path he took to achieve his life's goal was wrought with cruelty.